So... the basics, you need to make sure that the pool is big enough for fish, as you don't want an overcrowded pond. You also need to get a filter for the pond, and possibly an air pump and some air stones for hot days c:
But I am not sure about how long the pool would last, since you need to have real sturdy and strong bottom on your pond to avoid leakage. If you'd seriously want a pond, I'd suggest starting from zero, and getting yourself a good base. You could buy either some specially designed cloth for this purpose, or a glassfiber bottom
They sell them in many shapes and colors so you'd get the desired pond-look ;P But you could try out the pool first and see how it goes
You may also want to get some protective net or grid to put over the pond so no birds or cats will get your fish! I guess some thick, big plants around the sides would be nice too
Even if it's a pond, you'll need to do water changes and the like just like normal, but if you'll have a good filter there, you won't have to worry too much about that either. The water quality and temperature is harder to control in a pond, so you'd need to get hardy fish, like common goldfish, comets and shubunkins. I think fantails would be fine too, but no sensitive fancy varieties!
But about the feeding, you wouldn't need to feed any fish if you're just away for 2 days, especially NOT if they live in a pond d: There are always lots of bugs and the like that are out swimming for the fish to eat
Hope that helped a bit!
I'm not a pro on ponds but... at least I shared what I know